// code by isee15
// from https://github.com/isee15/Lunar-Solar-Calendar-Converter
//

package calendar

type Lunar struct {
	IsLeap     bool // 是否闰月
	LunarDay   int
	LunarMonth int
	LunarYear  int
}

type Solar struct {
	SolarDay   int
	SolarMonth int
	SolarYear  int
}

/**
*农历转公历
**/
func LunarToSolar(lunar Lunar) *Solar {
	var days = lunar_month_days[lunar.LunarYear-lunar_month_days[0]]
	var leap = getBitInt(days, 4, 13)
	var offset = 0
	var loopend = leap
	if !lunar.IsLeap {
		if lunar.LunarMonth <= leap || leap == 0 {
			loopend = lunar.LunarMonth - 1
		} else {
			loopend = lunar.LunarMonth
		}
	}
	for i := 0; i < loopend; i++ {
		offset += getBitInt(days, 1, 12-i) + 29
	}
	offset += lunar.LunarDay
	var solar11 = solar_1_1[lunar.LunarYear-solar_1_1[0]]
	var y = getBitInt(solar11, 12, 9)
	var m = getBitInt(solar11, 4, 5)
	var d = getBitInt(solar11, 5, 0)
	var solar = solarFromInt(solarToInt(y, m, d) + int64(offset-1))
	return solar
}

/**
*公历转农历
**/
func SolarToLunar(solar Solar) *Lunar {
	lunar := &Lunar{}
	var index = solar.SolarYear - solar_1_1[0]
	var data = (solar.SolarYear << 9) | (solar.SolarMonth << 5) | (solar.SolarDay)
	var solar11 = 0
	if solar_1_1[index] > data {
		index--
	}
	solar11 = solar_1_1[index]
	var y = getBitInt(solar11, 12, 9)
	var m = getBitInt(solar11, 4, 5)
	var d = getBitInt(solar11, 5, 0)
	var offset int = int(solarToInt(solar.SolarYear, solar.SolarMonth, solar.SolarDay) - solarToInt(y, m, d))
	var days = lunar_month_days[index]
	var leap = getBitInt(days, 4, 13)
	var lunarY = index + solar_1_1[0]
	var lunarM = 1
	var lunarD = 0
	offset += 1
	for i := 0; i < 13; i++ {
		dm := getBitInt(days, 1, 12-i) + 29
		if offset > dm {
			lunarM++
			offset -= dm
		} else {
			break
		}
	}
	lunarD = (int)(offset)
	lunar.LunarYear = lunarY
	lunar.LunarMonth = lunarM
	lunar.IsLeap = false
	if leap != 0 && lunarM > leap {
		lunar.LunarMonth = lunarM - 1
		if lunarM == leap+1 {
			lunar.IsLeap = true
		}
	}

	lunar.LunarDay = lunarD
	return lunar
}

var (
	lunar_month_days = [...]int{
		1887, 0x1694, 0x16aa, 0x4ad5, 0xab6, 0xc4b7, 0x4ae, 0xa56, 0xb52a,
		0x1d2a, 0xd54, 0x75aa, 0x156a, 0x1096d, 0x95c, 0x14ae, 0xaa4d, 0x1a4c, 0x1b2a, 0x8d55, 0xad4, 0x135a, 0x495d,
		0x95c, 0xd49b, 0x149a, 0x1a4a, 0xbaa5, 0x16a8, 0x1ad4, 0x52da, 0x12b6, 0xe937, 0x92e, 0x1496, 0xb64b, 0xd4a,
		0xda8, 0x95b5, 0x56c, 0x12ae, 0x492f, 0x92e, 0xcc96, 0x1a94, 0x1d4a, 0xada9, 0xb5a, 0x56c, 0x726e, 0x125c,
		0xf92d, 0x192a, 0x1a94, 0xdb4a, 0x16aa, 0xad4, 0x955b, 0x4ba, 0x125a, 0x592b, 0x152a, 0xf695, 0xd94, 0x16aa,
		0xaab5, 0x9b4, 0x14b6, 0x6a57, 0xa56, 0x1152a, 0x1d2a, 0xd54, 0xd5aa, 0x156a, 0x96c, 0x94ae, 0x14ae, 0xa4c,
		0x7d26, 0x1b2a, 0xeb55, 0xad4, 0x12da, 0xa95d, 0x95a, 0x149a, 0x9a4d, 0x1a4a, 0x11aa5, 0x16a8, 0x16d4,
		0xd2da, 0x12b6, 0x936, 0x9497, 0x1496, 0x1564b, 0xd4a, 0xda8, 0xd5b4, 0x156c, 0x12ae, 0xa92f, 0x92e, 0xc96,
		0x6d4a, 0x1d4a, 0x10d65, 0xb58, 0x156c, 0xb26d, 0x125c, 0x192c, 0x9a95, 0x1a94, 0x1b4a, 0x4b55, 0xad4,
		0xf55b, 0x4ba, 0x125a, 0xb92b, 0x152a, 0x1694, 0x96aa, 0x15aa, 0x12ab5, 0x974, 0x14b6, 0xca57, 0xa56, 0x1526,
		0x8e95, 0xd54, 0x15aa, 0x49b5, 0x96c, 0xd4ae, 0x149c, 0x1a4c, 0xbd26, 0x1aa6, 0xb54, 0x6d6a, 0x12da, 0x1695d,
		0x95a, 0x149a, 0xda4b, 0x1a4a, 0x1aa4, 0xbb54, 0x16b4, 0xada, 0x495b, 0x936, 0xf497, 0x1496, 0x154a, 0xb6a5,
		0xda4, 0x15b4, 0x6ab6, 0x126e, 0x1092f, 0x92e, 0xc96, 0xcd4a, 0x1d4a, 0xd64, 0x956c, 0x155c, 0x125c, 0x792e,
		0x192c, 0xfa95, 0x1a94, 0x1b4a, 0xab55, 0xad4, 0x14da, 0x8a5d, 0xa5a, 0x1152b, 0x152a, 0x1694, 0xd6aa,
		0x15aa, 0xab4, 0x94ba, 0x14b6, 0xa56, 0x7527, 0xd26, 0xee53, 0xd54, 0x15aa, 0xa9b5, 0x96c, 0x14ae, 0x8a4e,
		0x1a4c, 0x11d26, 0x1aa4, 0x1b54, 0xcd6a, 0xada, 0x95c, 0x949d, 0x149a, 0x1a2a, 0x5b25, 0x1aa4, 0xfb52,
		0x16b4, 0xaba, 0xa95b, 0x936, 0x1496, 0x9a4b, 0x154a, 0x136a5, 0xda4, 0x15ac,
	}
	solar_1_1 = [...]int{
		1887, 0xec04c, 0xec23f, 0xec435, 0xec649, 0xec83e, 0xeca51, 0xecc46, 0xece3a,
		0xed04d, 0xed242, 0xed436, 0xed64a, 0xed83f, 0xeda53, 0xedc48, 0xede3d, 0xee050, 0xee244, 0xee439, 0xee64d,
		0xee842, 0xeea36, 0xeec4a, 0xeee3e, 0xef052, 0xef246, 0xef43a, 0xef64e, 0xef843, 0xefa37, 0xefc4b, 0xefe41,
		0xf0054, 0xf0248, 0xf043c, 0xf0650, 0xf0845, 0xf0a38, 0xf0c4d, 0xf0e42, 0xf1037, 0xf124a, 0xf143e, 0xf1651,
		0xf1846, 0xf1a3a, 0xf1c4e, 0xf1e44, 0xf2038, 0xf224b, 0xf243f, 0xf2653, 0xf2848, 0xf2a3b, 0xf2c4f, 0xf2e45,
		0xf3039, 0xf324d, 0xf3442, 0xf3636, 0xf384a, 0xf3a3d, 0xf3c51, 0xf3e46, 0xf403b, 0xf424e, 0xf4443, 0xf4638,
		0xf484c, 0xf4a3f, 0xf4c52, 0xf4e48, 0xf503c, 0xf524f, 0xf5445, 0xf5639, 0xf584d, 0xf5a42, 0xf5c35, 0xf5e49,
		0xf603e, 0xf6251, 0xf6446, 0xf663b, 0xf684f, 0xf6a43, 0xf6c37, 0xf6e4b, 0xf703f, 0xf7252, 0xf7447, 0xf763c,
		0xf7850, 0xf7a45, 0xf7c39, 0xf7e4d, 0xf8042, 0xf8254, 0xf8449, 0xf863d, 0xf8851, 0xf8a46, 0xf8c3b, 0xf8e4f,
		0xf9044, 0xf9237, 0xf944a, 0xf963f, 0xf9853, 0xf9a47, 0xf9c3c, 0xf9e50, 0xfa045, 0xfa238, 0xfa44c, 0xfa641,
		0xfa836, 0xfaa49, 0xfac3d, 0xfae52, 0xfb047, 0xfb23a, 0xfb44e, 0xfb643, 0xfb837, 0xfba4a, 0xfbc3f, 0xfbe53,
		0xfc048, 0xfc23c, 0xfc450, 0xfc645, 0xfc839, 0xfca4c, 0xfcc41, 0xfce36, 0xfd04a, 0xfd23d, 0xfd451, 0xfd646,
		0xfd83a, 0xfda4d, 0xfdc43, 0xfde37, 0xfe04b, 0xfe23f, 0xfe453, 0xfe648, 0xfe83c, 0xfea4f, 0xfec44, 0xfee38,
		0xff04c, 0xff241, 0xff436, 0xff64a, 0xff83e, 0xffa51, 0xffc46, 0xffe3a, 0x10004e, 0x100242, 0x100437,
		0x10064b, 0x100841, 0x100a53, 0x100c48, 0x100e3c, 0x10104f, 0x101244, 0x101438, 0x10164c, 0x101842, 0x101a35,
		0x101c49, 0x101e3d, 0x102051, 0x102245, 0x10243a, 0x10264e, 0x102843, 0x102a37, 0x102c4b, 0x102e3f, 0x103053,
		0x103247, 0x10343b, 0x10364f, 0x103845, 0x103a38, 0x103c4c, 0x103e42, 0x104036, 0x104249, 0x10443d, 0x104651,
		0x104846, 0x104a3a, 0x104c4e, 0x104e43, 0x105038, 0x10524a, 0x10543e, 0x105652, 0x105847, 0x105a3b, 0x105c4f,
		0x105e45, 0x106039, 0x10624c, 0x106441, 0x106635, 0x106849, 0x106a3d, 0x106c51, 0x106e47, 0x10703c, 0x10724f,
		0x107444, 0x107638, 0x10784c, 0x107a3f, 0x107c53, 0x107e48,
	}
)

func getBitInt(data int, length int, shift int) int {
	return (data & (((1 << uint32(length)) - 1) << uint32(shift))) >> uint32(shift)
}

// WARNING: Dates before Oct. 1582 are inaccurate
func solarToInt(y int, m int, d int) int64 {
	m = (m + 9) % 12
	y = y - m/10
	return int64(365*y + y/4 - y/100 + y/400 + (m*306+5)/10 + (d - 1))
}

func solarFromInt(g int64) *Solar {
	var y = (10000*g + 14780) / 3652425
	var ddd = g - (365*y + y/4 - y/100 + y/400)
	if ddd < 0 {
		y--
		ddd = g - (365*y + y/4 - y/100 + y/400)
	}
	var mi = (100*ddd + 52) / 3060
	var mm = (mi+2)%12 + 1
	y = y + (mi+2)/12
	dd := ddd - (mi*306+5)/10 + 1
	var solar = &Solar{}
	solar.SolarYear = int(y)
	solar.SolarMonth = int(mm)
	solar.SolarDay = int(dd)

	return solar
}
